JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrapper">
    <br>
    <br>
    <div class="popover-test"></div>
    <div class="content"></div>
</div>

CSS

body {
    background-color:#ccc;
}
.wrapper {
    z-index:1;
}
.popover-test {
    background-color: #fff;
    border: 1px solid #929292;
    box-shadow: 0 0 10px 1px #929292;
    height: 100px;
    position: relative;
    width: 200px;
}
.popover-test::before {
    background-color: #fff;
    border-bottom: 1px solid #fff;
    border-top-left-radius: 4px;
    border-top-right-radius: 4px;
    top: -10px;
    content:"";
    height: 20px;
    left: 101px;
    width: 50px;
    position: absolute;
    z-index:1;
}
.popover-test::after {
    background-color: #fff;
    border: 1px solid #929292;
    border-bottom: 1px solid #fff;
    border-top-left-radius: 4px;
    border-top-right-radius: 4px;
    box-shadow: 0 0 10px 1px #929292;
    top: -20px;
    content:"";
    height: 20px;
    left: 100px;
    width: 50px;
    position: absolute;
    z-index:-1;
}